(1) Field of the Invention
The present invention relates generally to the dyeing of textiles and, more particularly, to a process for dyeing spandex-type elastomeric fibers.
(2) Description of the Prior Art
Spandex is a manufactured fiber in which a diisocyanate is reacted with a polyester. The fiber-forming substance is a long chain synthetic polymer comprised of at least 85% of a segmented polyurethane. The most commercially important spandex today is manufactured by DuPont and sold under the trademark LYCRA LUMAFLEX.RTM..
Spandex is lighter in weight, more durable, and more supple than conventional elastic yarn. It can be repeatedly stretched over 650% without breaking and recover instantly to its original length. It does not oxidize and is not damaged by body oils, perspiration, or detergents. Spandex is widely used for foundation garments, bathing suits, hosiery, webbing and fishing lures. However, while spandex can be dyed, the dyed spandex does not possess good fastness and will fail an AATCC Test Method 61-1975 IIA wash test.
U.S. Pat. No. 3,653,798, issued to Boardman, discloses a process for dyeing a blend of spandex and nylon in which a retarder is added to prevent the dye from partitioning strongly in favor of the nylon fibers. However, otherwise the fabric is dyed normally and there would be no expectation of improved IIA wash results.
It is also known to dye nylon fibers with acid or pre-metallized acid dyes which are exhausted in the presence of acetic or formic acid. However, while wetfastness is generally good, the dye does not cover barre and lightfastness varies.
Thus, there remains a need for a process for dyeing spandex-type elastomeric fibers which has a sufficient improvement in fastness as to enable the dyed fiber to pass a IIA wash test.